US3885100A - Six-port conference amplifier circuit - Google Patents

Six-port conference amplifier circuit Download PDF

Info

Publication number
US3885100A
US3885100A US474879A US47487974A US3885100A US 3885100 A US3885100 A US 3885100A US 474879 A US474879 A US 474879A US 47487974 A US47487974 A US 47487974A US 3885100 A US3885100 A US 3885100A
Authority
US
United States
Prior art keywords
circuits
bridge
amplifier
coupling
circuit
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US474879A
Other languages
English (en)
Inventor
James Richard Stidham
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
AT&T Corp
Original Assignee
Bell Telephone Laboratories Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Bell Telephone Laboratories Inc filed Critical Bell Telephone Laboratories Inc
Priority to US474879A priority Critical patent/US3885100A/en
Priority to CA215,819A priority patent/CA1010167A/en
Application granted granted Critical
Publication of US3885100A publication Critical patent/US3885100A/en
Priority to SE7505799A priority patent/SE399501B/xx
Priority to IT23722/75A priority patent/IT1038507B/it
Priority to BE156718A priority patent/BE829496A/xx
Priority to JP6259575A priority patent/JPS5444564B2/ja
Priority to DE2523620A priority patent/DE2523620C3/de
Priority to GB23390/75A priority patent/GB1505175A/en
Priority to NL7506454A priority patent/NL7506454A/xx
Priority to FR7516989A priority patent/FR2275947A1/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04M—TELEPHONIC COMMUNICATION
    • H04M3/00—Automatic or semi-automatic exchanges
    • H04M3/42—Systems providing special services or facilities to subscribers
    • H04M3/56—Arrangements for connecting several subscribers to a common circuit, i.e. affording conference facilities

Definitions

  • ABSTRACT [22] Filed: May 1974 Six transformer-coupled ports are connected in a hex- 21 Appl. No.: 474,879
  • agonal ring to form a telephone conference amplifier circuit.
  • Adjacent pairs of ports are directly, as well as resistance, connected to form three balanced bridges.
  • Each bridge has a differential amplifier which detects and amplifies signals originating in that bridge.
  • the output of each differential amplifier drives the common node between the other two bridges, thus coupling a signal into the other ports of the conference amplifier.
  • the new telephone conference amplifier circuit is a simple arrangement of inherent symmetry which offers a significant cost saving over conventional circuits.
  • This invention relates to telephone systems and. more particularly, to conference circuits which establish bilateral communication among a plurality of telephone subscriber lines.
  • a conference circuit which enables bilateral communication among three or more telephone subscriber lines generally imposes a number of requirements which are difficult to satisfy in the entiretyv Reliable communication among all the telephone subscriber lines, or conferees, requires maintenance of adequate signal levels. Regenerative circulation of signals among the conferees must be prevented even though impedance imbalances may exist among the telephone subscriber lines.
  • the performance of the conference circuit should be independent of the number of telephone subscriber lines connected in the conference. Due to these onerous and seemingly conflicting requirements, conference calls have heretofore necessitated relatively delicate and complex arrangements which usually employ specially designed coupling networks and/or a large number of amplifiers.
  • a principal object of the invention is to provide a telephone conference amplifier circuit of increased reliability at a saving in cost.
  • the present invention amply satisfies all of the foregoing requirements of telephone conference circuits simultaneously and does it, moreover, with a minimum of expense and circuit complexity.
  • the invention permits a conference connection of six ports serially arranged in a hexagonal ring. Three pairs of resistors which have substantially equal resistance are each respectively connected with adjacent pairs of ports to form three balanced bridge circuits.
  • Each bridge circuit includes a differential amplifier which detects and amplifies signals originating in that bridge. The output of each differential amplifier is applied to the common point between the other two bridges. thus coupling a signal from one port into the other ports of the conference amplifier circuit.
  • the secondaries of six transformer-coupled ports are serially connected in a hexagonal ring. Selected pairs of adjacent secondaries form one portion or side of balanced bridges that are each completed by two serially connected resistors disposed between the two outer nodes of each selected pair of secondaries. In all, three such bridge circuits are formed.
  • Each bridge circuit also includes a differential amplifier which has a first input connected to the common node between the selected pair of secondaries, and the other input connected to the common node between the two resistors completing that bridge. The output of each differential amplifier of a bridge circuit drives the common node between the two other bridge circuits. Each differential amplifier provides a high input impedance, a low output impedance, and a gain of two.
  • FIGURE is a schematic diagram of a sixport conference amplifier in accordance with the invention.
  • each of the designated ports in the FIGURE may be a termination point for a subscribers (i.e., conferees) telephone line.
  • Ports 1 through 6 each comprise a terminal pair connected to a primary circuit of one of the respective coupling networks, or transformers, II through 16.
  • the secondary circuits of transformers 11 through 16 are serially connected in a hexagonal ring. It is apparent from the FIG- URE that the secondary circuits of adjacent pairs of transformers, such as transformers 11 and 16, are also connected as two arms of a bridge circuit.
  • the first bridge circuit which includes transformers I1 and 16, is completed by serial resistors 19 and 21. Nodes l7 and 18 are located at the end" points of this bridge circuit.
  • a second bridge circuit comprises the secondary circuits of transformers l2 and 13 and serial resistors 22 and 23.
  • the node 18 is the common connection between the first and second bridge circuits.
  • the secondary circuits of transformers 14 and 15 along with serial resistors 26 and 27 comprise a third bridge circuit.
  • Node 24 is common to the second and third bridge circuits, while node 17 is common to the first and third bridge circuits.
  • Each bridge circuit also includes a differential amplifier.
  • the differential inputs of amplifiers 28, 29 and 31 are connected respectively to the first, second and third bridge circuits. It should be noted that all the amplifiers in the FIGURE are essentially identical. Furthermore, each of the amplifiers is selected to have a high input impedance, a low output impedance, and a voltage gain of two.
  • Each amplifier has two differential inputs that are connected to the balancing nodes of their respective bridge circuits (e.g., amplifier 28 is connected to nodes 32 and 33 of the first bridge).
  • the input terminals of each amplifier should be connected to the respective bridge circuit observing the same polarity.
  • the inverting input terminal of each amplifier is always shown connected to the resistance arm of each bridge circuit.
  • the output of each amplifier is coupled to the common node between the other two bridge circuits in the hexagonal ring.
  • transformers 11 through 16 are all the same electrically and each has a turns ratio between the primary and secondary windings in the neighborhood of one. All of the resistors in the FIGURE have a nominal resistance of approximately 6000, which serves to maintain balanced symmetry among the three bridge circuits of the conference amplifier.
  • the type of differential amplifiers selected for amplifiers 28, 29 and 3] should have high input impedance.
  • a typical high input impedance in this case, is approximately l5 k0. Furthermore, the output impedance of these amplifiers should be low (e.g., about [00). Finally, each amplifier should have a differential gain of about 6 dB and a common mode gain as low as practicable.
  • a variety of suitable integrated circuit differential amplifiers for the purposes of this invention are commercially available from many different manufacturers of integrated circuits.
  • any signal originating in port 1 or 6 will create a corresponding voltage potential across the secondary circuit of that port. Since nodes 17 and 18 are essentially at ground potential because the second and third bridge circuits are balanced, the low impedance outputs of amplifiers 29 and 31 serve to couple nodes 17 and 18 together by providing a low impedance signal path to ground. Accordingly, a signal originating from eitherv port 1 or 6 also appears at the other port via the interconnection of the secondary circuits of transformers l1 and 16.
  • the originating signal produces a voltage differential between nodes 32 and 33 which drives amplifier 28. It should be noted that because nodes 17 and 18 are held at ground potential, no voltage potential appears at node 33.
  • the output of amplifier 28, in turn, is applied to node 24 which is common to the second and third bridge cir cuits.
  • the output signal of amplifier 28 produces equal potential drops across the arms of the respective bridge circuits.
  • no potential difference is created for the inputs of amplifiers 29 and 31 and their outputs continue to remain at ground potential.
  • the voltage potential applied to node 24 divides equally between the series connected secondary circuits in the respective bridges. That is, the potential drop across each of the secondary circuits of transformers 12 and 13 is equal and half the potential value applied to node 24.
  • the same potential division occurs across the secondary circuits of transformers l4 and in the third bridge. With an amplification factor of two in amplifier 28 acting on the originating signal, a signal of the same level as the originating signal is thus available at the other output ports after the signal division. It is therefore apparent that any signal originating at port 1 or 6 creates a potential difference between nodes 32 and 33 which is amplified and applied to node 24 for the other two bridge circuits.
  • This signal is thus coupled to the other two bridge circuits of the amplifier.
  • signals originating at port 4 or 5 are coupled to each other and also applied to node 18 via amplifier 31 thereby coupling these signals to the first and second bridge circuits.
  • the operation of all three amplifiers which involves detecting the signals originating at their respective bridge circuits and coupling an amplified version thereof to the other bridge circuits, enables conference calls among all six ports of the conference amplifier.
  • the conference amplifier may be readily adapted for use with composite signaling set arrangements, which are conventional circuits in the telephone art, by replacing the coupling transformers therein with such arrangements.
  • This substitution conveniently provides a method of powering the subscriber line connected to the conference amplifier and of bypassing same for supervision signaling purposes.
  • a telephone conference amplifier circuit comprising six coupling means each one of which is associated with an external port, all of said coupling means internally connected in a hexagonal ring, three pairs of substantially equal value resistors, each said pair being respectively connected to the coupling means of adjacent pairs of ports to form three balanced bridge circuits, a differential amplifier means connected to each bridge circuit for detecting and amplifying signals originating in that bridge, and means for coupling the output of each amplifier means to the common point between the other two bridges, thus coupling a signal from one port into the other ports of the amplifier.
  • each of said coupling means is a transformer device having a primary winding connected to one of said external ports and a secondary winding serially connected in said hexagonal ring.
  • a telephone conference amplifier circuit comprising a plurality of coupling networks each having primary and secondary circuits, each of said primary circuits associated with a port, said secondary circuits all being connected in a series circuit such that a hexagonal ring is formed by said secondary circuits;
  • resistive means each having first, second and third terminals, said first terminal connected to one of the outer terminals of a pair of adjacent secondary circuits and said third terminal connected to the other outer terminal of said pair of adjacent secondary circuits such that three bridge circuits are formed each comprising an adjacent pair of secondary circuits and one of said resistive means;
  • each of said bridge circuits further including amplifytwo bridge circuits such that each primary circuit is coupled to all the other primary circuits.
  • each of said coupling networks is a transformer device 5.
  • each of said amplifying means is a differential amplifier and the one of said input terminals is a noninverting input while the other of said input terminals is an inverting input in relation to the phase of the output of each differential amplifier.
  • each of said differential amplifiers has a high input impedance, a low output impedanace, and a gain of two.

Landscapes

  • Engineering & Computer Science (AREA)
  • Multimedia (AREA)
  • Signal Processing (AREA)
  • Interconnected Communication Systems, Intercoms, And Interphones (AREA)
  • Telephonic Communication Services (AREA)
US474879A 1974-05-31 1974-05-31 Six-port conference amplifier circuit Expired - Lifetime US3885100A (en)

Priority Applications (10)

Application Number Priority Date Filing Date Title
US474879A US3885100A (en) 1974-05-31 1974-05-31 Six-port conference amplifier circuit
CA215,819A CA1010167A (en) 1974-05-31 1974-12-12 Six-port conference amplifier circuit
SE7505799A SE399501B (sv) 1974-05-31 1975-05-21 Konferenskrets
BE156718A BE829496A (fr) 1974-05-31 1975-05-26 Circuit de conference
IT23722/75A IT1038507B (it) 1974-05-31 1975-05-26 Circuto amplificatore di comunica zione circolare a sei terminali
JP6259575A JPS5444564B2 (enExample) 1974-05-31 1975-05-27
DE2523620A DE2523620C3 (de) 1974-05-31 1975-05-28 Konferenzschaltung
GB23390/75A GB1505175A (en) 1974-05-31 1975-05-29 Telephone conference circuit
NL7506454A NL7506454A (nl) 1974-05-31 1975-05-30 Telefoon-conferentie-schakeling.
FR7516989A FR2275947A1 (fr) 1974-05-31 1975-05-30 Circuit de conference comprenant plusieurs circuits de couplage

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US474879A US3885100A (en) 1974-05-31 1974-05-31 Six-port conference amplifier circuit

Publications (1)

Publication Number Publication Date
US3885100A true US3885100A (en) 1975-05-20

Family

ID=23885317

Family Applications (1)

Application Number Title Priority Date Filing Date
US474879A Expired - Lifetime US3885100A (en) 1974-05-31 1974-05-31 Six-port conference amplifier circuit

Country Status (10)

Country Link
US (1) US3885100A (enExample)
JP (1) JPS5444564B2 (enExample)
BE (1) BE829496A (enExample)
CA (1) CA1010167A (enExample)
DE (1) DE2523620C3 (enExample)
FR (1) FR2275947A1 (enExample)
GB (1) GB1505175A (enExample)
IT (1) IT1038507B (enExample)
NL (1) NL7506454A (enExample)
SE (1) SE399501B (enExample)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4163871A (en) * 1977-12-22 1979-08-07 International Telephone And Telegraph Corporation Digital CVSD telephone conference circuit

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE3144267C2 (de) * 1981-11-07 1984-08-30 Felten & Guilleaume Fernmeldeanlagen GmbH, 8500 Nürnberg Verfahren und Schaltungsanordnung zum Aufbau von Konferenzverbindungen in Fernmeldeanlagen

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1944283A (en) * 1929-06-22 1934-01-23 Siemens Ag Telephone interconnecting circuit
US3108157A (en) * 1959-06-15 1963-10-22 Bell Telephone Labor Inc Multiple station communication circuit
US3527889A (en) * 1967-03-01 1970-09-08 New North Electric Co Conference communication system
US3767861A (en) * 1972-08-31 1973-10-23 Gte Automatic Electric Lab Inc 3 to 10 port conference circuit
US3816917A (en) * 1971-06-30 1974-06-18 Post Office Telephone conference amplifier
US3824344A (en) * 1973-03-22 1974-07-16 Bell Telephone Labor Inc Conference bridge circuit

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS494764A (enExample) * 1972-04-27 1974-01-16

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1944283A (en) * 1929-06-22 1934-01-23 Siemens Ag Telephone interconnecting circuit
US3108157A (en) * 1959-06-15 1963-10-22 Bell Telephone Labor Inc Multiple station communication circuit
US3527889A (en) * 1967-03-01 1970-09-08 New North Electric Co Conference communication system
US3816917A (en) * 1971-06-30 1974-06-18 Post Office Telephone conference amplifier
US3767861A (en) * 1972-08-31 1973-10-23 Gte Automatic Electric Lab Inc 3 to 10 port conference circuit
US3824344A (en) * 1973-03-22 1974-07-16 Bell Telephone Labor Inc Conference bridge circuit

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4163871A (en) * 1977-12-22 1979-08-07 International Telephone And Telegraph Corporation Digital CVSD telephone conference circuit

Also Published As

Publication number Publication date
DE2523620A1 (de) 1975-12-11
NL7506454A (nl) 1975-12-02
BE829496A (fr) 1975-11-26
DE2523620C3 (de) 1981-09-10
FR2275947A1 (fr) 1976-01-16
DE2523620B2 (de) 1980-11-27
JPS5444564B2 (enExample) 1979-12-26
FR2275947B1 (enExample) 1977-07-22
GB1505175A (en) 1978-03-30
IT1038507B (it) 1979-11-30
SE7505799L (sv) 1975-12-01
JPS513503A (enExample) 1976-01-13
SE399501B (sv) 1978-02-13
CA1010167A (en) 1977-05-10

Similar Documents

Publication Publication Date Title
US3855430A (en) Electronic hybrid circuit for two-wire to four-wire interconnection
US2742616A (en) Negative impedance repeaters
US3824344A (en) Conference bridge circuit
JPS5921237B2 (ja) 電話ライン回路
US4380690A (en) Hybrid circuit
US3855431A (en) Electronic hybrid amplifier
US3885100A (en) Six-port conference amplifier circuit
US4914693A (en) Telephone subscriber circuit
US3083265A (en) Conference call circuit
US3991279A (en) Monobus interface circuit
US3586881A (en) Transistor hybrid circuit
GB1563658A (en) Interface circuits
US3991280A (en) Monobus variable resistance transmission circuit
JPH0159767B2 (enExample)
US3875350A (en) Self-balancing hybrid circuit
US3524929A (en) Telephone conference circuit
US3627952A (en) Direct current reduction network for amplification telephone sets
US1944283A (en) Telephone interconnecting circuit
US3767861A (en) 3 to 10 port conference circuit
US4682355A (en) Electronic feeding bridge for a space division switching network
US3904838A (en) Two-wire, bi-directional voice frequency repeater
US3511931A (en) Conferencing networks employing virtual ground summation to obtain isolation
CA1240089A (en) Circuit for maintaining hybrid cancellation of signals in a communication system
US2260170A (en) Transmission system embodying loud-speakers
US3636266A (en) Negative impedance line isolators